Scala中List、Map、Set各类型操作汇总

1、Scala中List、Map、Set等各类型函数操作汇总

package com.scala.study

import scala.collection.immutable.{Queue, TreeMap}
import scala.collection.mutable

/**
  * Created by HP-PC on 2016/5/26.
  */

object ScalaCaseDemo {
  def main(args: Array[String]): Unit = {
    println(1 :: 2 :: List(3, 4)) //单个元素联合List：List(1, 2, 3, 4)
    //两个List进行联合成一个List：List(1, 2, 3, 4)
    println(List(1, 2) ::: List(3, 4))
    println(List("Spark", "Hadoop", "Hive").head) //Spark
    println(List("Spark", "Hadoop", "Hive").tail) //List(Hadoop, Hive)
    //将List集合拆分成2个List集合：(List(1,2,3),List(4,5,6))
    println(List(1, 2, 3, 4, 5, 6).span(_ < 4))
    //将List集合中的元素用"-"进行拼接
    println(List("a", "b", "c", "d").mkString("_"))
    //将List集合元素进行拆分，合并成一个大的List集合
    println(List("Spark", "Hadoop").flatMap(_.toList))
    //exists判断List集合中是否存在元素，forall是判断整行情况
    println(List(List(1, 0, 0), List(0, 1, 0), List(0, 0, 0)).exists(row => row.forall(_ == 0)))

    /**
      * foldLeft就是每次计算的结果加上List集合中的元素
      * 如：1+0=1,2+1=3,3+3=6,4+6=10，5+10=15，...=5050
      */
    println((1 to 100).toList.foldLeft(0)(_ + _))

    /**
      * foldRight就是每次List集合中的元素减去计算结果
      * 如：1-100 = -99,2-(-99) = 101,3-101 = -98,4-(-98) = 102,5-102 = -97
      */
    println(List(1, 2, 3, 4, 5).foldRight(100)(_ - _))
    println(List.apply(1, 2, 3, 4, 5))
    println(List("b", "e", "a", "f").sortWith(_ < _)) //List排序输出
    println(List.make(3, 5)) //构造List重复元素：List(5,5,5)
    println(List.range(1, 5)) //List(1,2,3,4)
    println(List.range(1, 9, 3)) //List中的元素是按间隔生成：List(1,4,7)
    //拉链操作：List((a,1), (b,2), (c,3), (d,4), (e,5))
    val zipped = "abcde".toList zip List(1, 2, 3, 4, 5)
    println(zipped)
    println(zipped.unzip) //解拉链：(List(a, b, c, d, e),List(1, 2, 3, 4, 5))
    //List集合进行合并：List(1, 2, 3, 4, 5)
    println(List(List(1, 2), List(3, 4), List(5)).flatten)
    //List集合进行合并：List(1, 2, 3, 4, 5)
    println(List.concat(List(1, 2), List(3, 4), List(5)))
    //两个List按给定的函数进行操作：List(300, 1200)
    println(List.map2(List(100, 200), (List(3, 6)))(_ * _))

    val empty = Queue[Int]()
    val queue1 = empty.enqueue(1)
    val queue2 = queue1.enqueue(List(2, 3, 4, 5))
    println(queue2)
    val (element, left) = queue2.dequeue
    println(element + ":" + left)

    //创建可变Set
    val data = mutable.Set.empty[Int]
    data ++= List(2, 3, 4)
    data += 4 //Set:重复数据不会添加
    println(data)
    data --= List(2, 3) //移除List集合
    println(data)
    data.clear() //清空Set集合
    println(data)

    //创建可变Map
    val map = mutable.Map.empty[String, String]
    map("Java") = "Hadoop"
    map += {
      "Scala" -> "Spark"
    }
    map += ("Scala" -> "Tachyon") //相同Key，value值覆盖
    println(map)
    println(map("Java"))
    for ((k, v) <- map) println(k + ":" + v)

    //创建treeSet，输出是按升序排序的
    val treeSet = mutable.TreeSet(9, 2, 3, 8, 6, 7, 5, 1)
    treeSet += 4
    println(treeSet)
    val treeSetForStr = mutable.TreeSet("Spark", "Hadoop", "Kafka", "Tachyon")
    println(treeSetForStr)

    //创建treeMap
    val treemap = TreeMap("Scala" -> "Spark", "Java" -> "Hadoop")
    println(treemap)
  }
}